Rubber compositions modified with hydroxy-benz-imidazole oxides

ABSTRACT

It now has been found that the properties of rubber compositions comprising rubbers having an unsaturated carbon chain can be improved by including therein, a minor property-improving amount of at least one hydroxy-benzimidazole oxide compound of the formula ##STR1## wherein R is hydrogen, or a halogen, hydroxyl, lower acyl, lower hydrocarbyl, lower hydrocarbyloxy, lower hydrocarbylthio, carboxyl, cyano, amino, amide or --C(O)-- lower hydrocarbyl group, and R&#39; is hydrogen, or a lower hydrocarbyl, lower hydrocarbyl amide, carboxamide carboxy acid, carboxy ester, or aryl group. When vulcanizates are prepared from such rubber compositions containing one or more fillers, the vulcanizates exhibit reduced low strain hysteresis and a high electrical resistivity. 
     In another aspect of the invention, a filled vulcanizate made by vulcanizing uncured compositions of the type described above and containing a filler, particularly carbon black, is improved in filler interaction, hysteresis, modulus, compression set and resiliency. Rubber articles and portions thereof such as tires, hoses, springs, belts, treads, sidewalls and the like can be made utilizing the improved filled vulcanizates of the invention.

TECHNICAL FIELD OF THE INVENTION

This invention relates to uncured rubber compositions, filledvulcanizates, and rubber articles such as tire, treads, sidewalls,hoses, belts, springs, etc. made therefrom. More particularly, itrelates to rubber compositions exhibiting improved properties andcontaining one or more hydroxy-benzimidazole oxides. The invention alsorelates to articles made from such vulcanizates such as tires, andmethods of reducing the rolling loss and running temperatures of suchtires.

BACKGROUND OF THE INVENTION

It is known that rubber compositions generally are combined or"compounded" with various other materials before being cured and/or putinto use. Some of these added materials through chemical and/or physicalinteraction with the rubber improve the properties of the end product inservice while others improve processing properties of the uncuredcompositions. In some instances, both effects may be achieved. It isalso known that the various chemicals, pigments and other materials soused, both organic and inorganic, can interact in various ways toproduce desirable or deleterious effects. For further discussions ofrubber processing and materials used therein, see, for example,Encyclopedia of Polymer Science and Technology, Second Edition,published by John Wiley and Sons, New York (1970), particularly Vol. 12,page 280 and The Vanderbilt Rubber Handbook, R. T. Vanderbilt Company,Norwalk, Conn., 06855 (1968), particularly Sections 6, 7, 8, 9 and 11.

Vulcanizing agents, plasticizers, extenders, accelerators, fillers,pigments, etc. generally are incorporated into vulcanizable rubbercompositions so that the rubber can be cured or vulcanized in a mold toform useful articles. It often is necessary to include processing aidsin rubber compounds prior to molding and curing. These aids areprimarily intended to improve the mixing of the ingredients of therubber compound, the processability of the rubber, the mold or millrelease properties of the rubber, tack and green strength withoutseriously adversely affecting the properties of the cured rubber.

Vulcanizing or curing agents used in vulcanizable rubbers generally aresulfur or sulfur-containing compounds or peroxide compositions. The rateof the vulcanization reaction generally is slow with many rubbermaterials unless an accelerator is incorporated into the vulcanizablemixture. A number of materials have been suggested and utilized fortheir accelerating effect. Such materials include metal oxides, forexample, lead oxide, calcium oxide and magnesium oxide. Organicaccelerators have found wide use in today's technology, and many ofthese are derivatives of aniline. A large portion of the organicvulcanization accelerators which are in current use are derivatives of2-mercaptobenzothiazole (MBT). One group of MBT derivatives which hasfound wide acceptance includes the N-derivatives of 2-benzothiazolesulfenamide. A number of such derivatives and their use as acceleratorsof vulcanization are described and discussed in Vol. 20 of theEncyclopedia of Chemical Technology, Kirk-Othmer editors, Third Edition,1983, pp. 337-363. See also U.S. Pat. No. 2, 367,827.

In order to minimize or eliminate premature curing of the rubberformulation (scorching), the vulcanizing agents and accelerators areadded to the formulation just prior to the curing step. The othernormally used rubber formulation additives are mixed with the baserubber compositions in, for example, a masterbatch operation, prior tocontact with the sulfur and accelerator.

Fillers such as carbon blacks, glass, silica, talc, and other finelydivided inorganic materials are used in rubber formulations and varywidely as to their characteristics and combinations of characteristics.In rubber formulations, carbon black and/or silica are used asreinforcing fillers. Many carbon blacks of the channel and furnace typeswith varying characteristics have been utilized because they impartvarying desirable characteristics to the rubber. The formation of asecondary network structure in rubber stocks containing reinforcingcarbon blacks leads to high hysteresis at low deformations. Variousadditives have been suggested in the art to reduce the hysteresis ofsuch rubber stocks.

As mentioned, the present invention relates to tires having low rollingresistance. Since the tread portion of a tire is adapted to be groundcontacting and occupies a considerable portion of the tire thereof, itis advantageous to use a tread composition which will produce a treadhaving desirable properties. Rubber compositions which will producetires having a small hysteresis loss due to deformation of the tireswhen they are rolled have been used in the industry in attempts toobtain tires having decreased rolling resistance. Conventional treadcompositions normally are composed of materials which tend to increasehysteresis loss in the resulting treads.

One of the difficulties of producing tire treads having decreasedhysteresis loss is the potential resulting loss of other desirableproperties such as braking performance wet and dry traction, and wearresistance. Thus, it is desirable to develop rubber formulations usefulin making the treads of tires which reduce the hysteresis loss of thetreads without impairing braking performance, traction, wear resistanceand other desirable properties.

SUMMARY OF THE INVENTION

It now has been found that the properties of rubber compositionscomprising rubbers having an unsaturated carbon chain can be improved byincluding therein, a minor property-improving amount of at least one1-hydroxy-benzimidazole 3-oxide compound of the formula ##STR2## whereinR is hydrogen, or a halogen, hydroxyl, lower hydrocarbyl, lowerhydrocarbyloxy, lower hydrocarbylthio, carboxyl, cyano, amino, amide or--C(O)-- lower hydrocarbyl group, and R' is hydrogen, or a lower acyl,lower hydrocarbyl, lower hydrocarbyl amide, carboxamide carboxy acid,carboxy ester, or aryl group.

In another aspect of the invention, a filled vulcanizate made byvulcanizing uncured compositions of the type described above andcontaining a filler, particularly carbon black, is improved in fillerinteraction, hysteresis, modulus, compression set and resiliency. Rubberarticles and portions thereof such as tires, hoses, belts, treadsidewalls and the like can be made utilizing the improved filledvulcanizates of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The rubber compositions in one embodiment of this invention are notcured. In other words, they are not vulcanized. In one embodiment of theinvention, the uncured rubber compositions of the present invention aremodified rubber compositions which comprise (a) at least one rubberhaving an unsaturated carbon chain, and (b) a minor, curedproperty-improving amount of at least one 1-hydroxy-benzimidazole3-oxide compound of the formula ##STR3## wherein R is hydrogen, or ahalogen, hydroxyl, lower hydrocarbyl, lower hydrocarbyloxy, lowerhydrocarbylthio, carboxyl, cyano, amino, amide or --C(O)-- lowerhydrocarbyl group, and R' is hydrogen, or a lower acyl, lowerhydrocarbyl, lower hydrocarbyl amide, carboxamide carboxy acid, carboxyester, or aryl group. It is preferred that R is in the 5- or 6-position.

In another embodiment the rubber compositions are modified rubbercompositions containing a minor, cured property-improving amount of atleast one nitrogen- and oxygen-containing composition made by thereaction of a primary nitroalkene (R'CH₂ NO₂), a beta-ketosulfone (e.g.,PhSO₂ C(R')HC(O)Ph) or an alpha-sulfonyl carboxylic ester andcarboxamide (e.g., PhSO₂ CH₂ R') with a benzofurazan oxide in thepresence of an alkali, said benzofurazan oxide being characterized bythe formula ##STR4## wherein R is hydrogen, or a halogen, hydroxyl,lower hydrocarbyl, halohydrocarbyl lower hydrocarbyloxy, lowerhydrocarbylthio, carboxyl, cyano, amino, amide or --C(O)-- lowerhydrocarbyl group.

The rubbers in another aspect of this invention are vulcanizates (i.e.,cured stocks) prepared by vulcanizing an uncured rubber mixture of thetype described above and which includes at least one filler. In additionto fillers of the conventional type such as carbon black and otherinorganic, finely divided materials contained in uncured rubbers, thevulcanizates contain conventional curing systems and agents, such assulfur, antioxidants, accelerators, retarders, coupling agents,promoters and the like.

The rubbers used herein contain carbon-carbon unsaturation in themolecular structure and these rubbers include natural as well assynthetic rubbers. The rubber compositions used in the present inventioninclude natural rubber and rubber-like polymers produced by polymerizingaliphatic, conjugated diolefins, especially those containing 4 to 8carbon atoms per molecule such as butadiene, isoprene, pentadienes,etc., or the copolymers of such dienes. The rubbers used in the uncuredcompositions of this invention have unsaturated carbon chains. That is,their polymer backbones contain a significant amount of unsaturation, incontrast to the pendant or vinyl saturation found in some other types ofrubbers. Typically, the chains of such unsaturated rubbers have at leastabout 5% of their carbon-to-carbon bonds as unsaturated bonds.Characterization of rubber as having unsaturated carbon chains is wellknown in the art as shown by ANSI/ASTM Standard D 1418-79A whereunsaturated-chain rubbers are referred to as R rubbers. Class R rubbersinclude natural rubber and various synthetic rubbers derived at leastpartly from diolefins. The following is a non-exclusive list of R classrubbers which can be used in the compositions of the present invention:

ABR--Acrylate-butadiene

BR--Butadiene

CIIR--Chloro-isobutene-isoprene

CR--Chloroprene

IR--Isoprene, synthetic

NBR--Nitrile-butadiene

NCR--Nitrile-chloroprene

NIR--Nitrile-isoprene

NR--Natural rubber

SBR--Styrene-butadiene

SCR--Styrene-chloroprene

SIR--Styrene-isoprene rubbers

Of these, the NR, IR, BR, SBR or mixtures of two or more of these aretypically used. Many compositions are made wherein the rubber is NR, SBRor a mixture containing at least about 50% of one of these. Compositionscontaining only NR as the rubber portion are often used. In the contextof this invention, NR includes both hevea and guayule rubber as well asmixtures thereof.

The rubbers used herein having carbon-carbon unsaturation also may beother than the above-described R rubbers. Examples of such rubbersinclude EPDM. EPDM rubbers are derived from ethylene-propylenedienemonomer and generally about 3-8% of their carbon bonds are unsaturatedbonds.

The above rubber compositions can be modified in accordance with thepresent invention by incorporating into the rubber a minorproperty-improving amount of at least one hydroxy-benzimidazole oxidecompound or the nitrogen- and oxygen-containing reaction products asdefined and illustrated more fully below. The amount of these additivesincorporated into the unvulcanized rubber composition will generally bean amount which is sufficient to provide desirable properties to therubber composition in its cured form. Thus, the amount of thebenzimidazole and/or nitrogen- and oxygen-containing reaction productincorporated into an uncured formulation will be an amount which willimprove the processability of the composition, and in certain instances,its green strength and/or viscosity properties. Processabilityproperties are those related to the ease and efficiency of mixing,mastication and handling of a rubber composition in its unvulcanized,that is, uncured state. Similar amounts used in the cured compositionsto improve such vulcanizate properties as filler interaction,hysteresis, rolling loss, running temperature and the like. Typically,this property-improving amount will range from about 0.1 to about 10parts per 100 parts by weight of rubber (phr). More often, amountsranging from about 0.5 to 5 phr are included in the rubber compositions.

In one embodiment, the hydroxy-benzimidazole oxides used in both thevulcanizable and vulcanized (cured) rubber compositions of thisinvention are characterized by the formula ##STR5## wherein R ishydrogen, or a halogen, hydroxyl, lower hydrocarbyl, lowerhydrocarbyloxy, lower hydrocarbylthio, carboxyl, cyano, amino, amide or--C(O)-- lower hydrocarbyl group, and R' is hydrogen, or a lower acyl,lower hydrocarbyl, lower hydrocarbyl amide, carboxamide carboxy acid,carboxy ester, or aryl group. In a preferred embodiment, R is in the 5-or 6-position.

The hydrocarbyl groups R and R' may be alkyl, aryl, alkaryl, aralkyl,etc., and the hydrocarbyloxy groups may be the corresponding alkoxy,aryloxy, etc. groups. More generally, the hydrocarbyl groups are loweralkyl group containing up to about 8 carbon atoms such as methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, pentyl, etc. It is preferredthat R is hydrogen, methyl, or methoxy, and in a particularly preferredembodiment, R is hydrogen.

It is preferred that R' is hydrogen or a lower hydrocarbyl as definedabove, and generally, R' is a lower hydrocarbyl such as a methyl orethyl group.

The hydroxy-benzimidazole oxides useful in this invention andrepresented by Formula I can be prepared by methods known in the art.For example, benzimidazoles can be prepared by the reaction ofbenzofurazan oxides (II) with a primary nitroalkane, a beta-ketosulfone,an alpha-sulfonyl carboxylic acid ester, or an alpha-sulfonylcarboxamide, said benzofurazan oxide being characterized by thefollowing Formula II ##STR6## wherein R is hydrogen, or a halogen,hydroxyl, lower hydrocarbyl, halohydrocarbyl lower hydrocarbyloxy, lowerhydrocarbylthio, carboxyl, cyano, amino, amide or --C(O)-- lowerhydrocarbyl group. Such reactions are described in the literature andare reported to form 1-hydroxy benzimidazole 3-oxides and possibly minoramounts of other nitrogen- and oxygen-containing materials. Compositionscomprising such reaction products including the 1-hydroxy-benzimidizole3-oxides of Formula I are useful by modifying the rubbers in accordancewith the process of the present invention. For convenience, the reactionof the benzofurazan oxide with a primary nitroalkane, abeta-ketosulfone, or an alpha-sulfonyl carboxylic acid ester orcarboxamide is represented below as forming the 1-hydroxy-benzimidazole3-oxide. ##STR7## R'CH₂ NO₂ ; R'=H, hydrocarbyl, hydrocarbyl amide,carboxy ester; or

PhSO₂ C(R')HC(O)Ph; R'=H, hydrocarbyl; or

PhSO₂ CH₂ R'; R'=carboxamide, carboxy ester.

The reactions are conducted in the presence of a base.

The procedure for preparing 1-hydroxy-1-H-benzimidazole 3-oxides by thereaction of about equimolar amount of benzofurazan oxide with primarynitroalkanes such as represented by the formula

    R'CH.sub.2 NO.sub.2

in tetrahydrofuran in the presence of organic amine bases attemperatures of from about ambient temperature up to about 50°-60° C. isdescribed in the literature such as, for example, J. Org. Chem., Vol.37, No. 15, 1972, pp. 2519-2520, and A. Gasco and A. J. Boulton,Advances in Heterocyclic Chemistry, Vol. 29, pp. 310-311, Academic Press1981. The contents of these publications are hereby incorporated byreference for their disclosures of the preparation of1-hydroxy-benzimidazole oxides useful in the present invention.

Briefly, benzofurazan oxide reacts exothermically with primarynitroalkanes in tetrahydrofuran and in presence of organic amine basesto form the desired 2-substituted 1-hydroxy-benzimidazole 3-oxides andnitrite salts of the amines. For example, if diethylamine is used as thebase, the by-product is the nitrite of diethylamine.

In the typical procedure, 0.1 mole of benzofurazan 1-oxide and 0.12 moleof nitroethane is dissolved at 100 ml. of tetrahydrofuran. To thismixture there is added at room temperature, 0.12 mole of diethylamineover a period of 0.5 hour. An instantaneous exothermic reaction isobserved (40° C.) and within one hour, the product crystallizes from thesolution. The solution is allowed to stand overnight at room temperatureand filtered to yield 9.6 grams of 2-methyl-1-hydroxy-1-H-benzimidazole3-oxide (Table I, Example 2). The product can be rectystallized frommethanol.

The preparation of hydroxy-benzimidazole 3-oxides useful in the presentinvention by reaction of about equimolar amounts of benzofurazan oxidewith beta-ketosulfones alpha-sulfonyl carboxamides, and alpha-sulfonylcarboxylic esters in an alkaline medium at temperatures of from ambienttemperature to about 50°-60° C. is described in J. Org. Chem., Vol. 37,No. 15, 1972, pp. 2372-2376, and A. Gasco and A. J. Boulton, Advances inHeterocyclic Chemistry, Vol. 29. pp. 310-311, Academic Press 1981. Thecontents of the references are hereby incorporated for the disclosure ofthe preparation of various benzimidazole oxides useful in the presentinvention.

Examples of beta-ketosulfones which can be reacted with benzofurazanoxides in alkaline media include 2-benzene sulfonyl acetophenone, and2-alkyl-2-benzene sulfonyl acetophenones wherein the alkyl group is, forexample, a lower hydrocarbyl group such as methyl, ethyl, butyl, etc.Examples of alpha-sulfonyl carboxamides which can be reacted withfurazan oxides include 2-benzene sulfonyl acetamides wherein R' may be--C(O)NH₂ ; --C(O)NHPh; --C(O)N(Et)2; --C(O)N(i--Pr)2; --C(O)NCH₃ Ph;--C(O)OH; and --C(O)OEt. The base utilized to promote the reactiongenerally is an alkali metal hydroxide such as sodium or potassiumhydroxide dissolved in an alcohol such as methanol or ethanol. Anexample of an alpha-sulfonyl carboxylic ester which can be reacted withbenzofurazan oxides is ethyl 2-benzene sulfonyl acetate.

The general procedure for the reaction of benzofurazan oxide withbeta-carbonyl sulfones is as follows: A mixture of 0.02 mole of thebeta-carbonyl sulfone, 5.44 grams (0.04 mole) of benzofurazan oxide and50 ml. of methanol is prepared and crystals are dissolved by warming themixture. An 8% methanolic KOH solution (50 ml.) is added and the mixturemaintained at room temperature for 12 hours. The reaction mixture isfiltered, and the filtrate is evaporated to dryness whereupon 15 ml. ofwater is added to the residue. Stirring and cooling results in thecrystallization of potassium salt by-products, and the mixture isfiltered. This filtrate is neutralized with concentrated hydrochloricacid until a few droplets of oil are formed. The oil is extracted withether and the aqueous layer separated and neutralized further withconcentrated hydrochloric acid to form an oily precipitate. Theprecipitate is triturated with acetone to give fairly pure crystals ofthe 1-hydroxy-3-oxobenzimidazole derivatives. The products are solublein acidic and basic media and insoluble in acetone. The products can berecrystallized from methanol, ethanol, and/or water.

When 2-alkyl-2-benzene sulfonyl acetophenones are reacted with abenzofurazan oxide, when the reaction mixture is warmed to 40°-60° C.for 8 hours and then worked up as described above. The reaction mixtureis prepared utilizing 2-benzene sulfonyl acetamide (R'=CONH₂) is warmedfor 30 minutes and then worked up as described above.

The reaction mixture of benzofurazan oxide with ethyl 2-benzene sulfonylacetate is warmed to 50° C. for 3 hours, and the resulting1-hydroxy-3-oxobenzimidazole-2-carboxylic acid is recrystallized bydissolving it several times in 1% KOH solution and neutralizing withhydrochloric acid.

Compounds corresponding to Formula I wherein R' is an aryl group, andmore specifically where R' is a phenyl group can be prepared fromnitroso and nitrile oxide compounds as described in Houben Weyl,Methoden der Organischen Chemie, vol. X/III, page 868. ##STR8##

The rubber compositions also can be modified in accordance with oneembodiment of this invention by including in the rubber, aproperty-improving amount of the product or product mixture obtained inthe above described reaction of benzofurazan oxides (II) with theabove-described reagents. Although preferred, it is not essential thatthe products identified as (I) above be isolated from the remainder ofthe reaction products.

Specific examples of 1-hydroxy-benzimidazole 3-oxides which can be usedto modify rubber compositions in accordance with this invention areillustrated in the following Table I.

                  TABLE I                                                         ______________________________________                                        1-Hydroxybenzimidazole 3-Oxides                                                ##STR9##                                                                     Example       R     R'                                                        ______________________________________                                        1             H     H                                                         2             H     CH.sub.3                                                  3             H     CH.sub.2 CH.sub.3                                         4             H     CH.sub.2 CH.sub.2 CONH.sub.2                              5             H     CO.sub.2 CH.sub.2 CH.sub.3                                6             H     CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.3                       7             H     CONH.sub.2                                                8             H     CON(C.sub.2 H.sub.5).sub.2                                9             H     CON(iPr).sub.2                                            10            H     COOEt                                                     11            H     C(O)N(CH.sub.3)Ph                                         12            H     C(O)NHPh                                                  13            H     C.sub.6 H.sub.5                                           14            H                                                                                    ##STR10##                                                ______________________________________                                    

EXAMPLES 13-24

These compounds are similar to Examples 1-12 except R is --CH₃ in lieuof H.

The vulcanizable compositions of the present invention comprising atleast one rubber and at least one 1-hydroxy-benzimidazole oxide compoundand/or the above-described nitrogen- and oxygen-containing compositionscan be prepared by conventional techniques using various types of mills,blenders and mixers known to the art. The temperatures used informulating the rubber compositions of this invention range from ambientto those normally used in the art such as 75° to 175° or 220° C.

Specifically, devices such as well-known Brabender and Banbury mixerscan be used to mechanically compound the rubber and the1-hydroxy-benzimidazole oxides or nitrogen- and oxygen-containingreaction products described above together with any fillers such ascarbon black, and other materials generally used in conventional rubberformulations such as antioxidants, retarders, etc. as mentioned above.To achieve the improved properties, the vulcanizable mixtures of thepresent invention are compounded at temperatures of about 95° to 205° C.(200°-400° F.), typically, about 160°-200° C. (325°-390° F.) for aperiod of from about 2 to about 20 minutes, generally from about 3 toabout 15 minutes. For example, when a conventional size Banbury mixer isused, the apparatus is operated at a rotor speed of about 50 to about150 rpm. while a laboratory 65 cc. Brabender apparatus is operated at amixing speed of about 60-100 rpm. Such devices can be equipped withthermocouples and water jackets to monitor and control mixing batchtemperature. Finishing steps can be carried out on conventionalequipment such as open mills using conditions and techniques known tothe art. Similarly, tread components for pneumatic tires can be preparedby conventional procedures.

In some instances, it is convenient to combine the1-hydroxy-benzimidazole oxide with an inert material which serves as acarrier and de-sensitizer. Organic materials such as methyl stearate,petroleum wax, viscous mineral oils as well as inorganic and mixedmaterials such as clay, zinc stearate, diatomaceous earth and the likecan be used for this purpose. Such combinations usually contain about25-95% of the 1-hydroxy-benzimidazole oxide with the balance being oneor more of the inert materials.

In addition to the 1-hydroxy-benzimidazole oxides or nitrogen- andoxygen-containing reaction products, the uncured rubber compositions ofthis invention also may contain materials used in conventional rubberformulations such as antioxidants, retarders, promoters, fillers, etc.In the uncured or unvulcanized rubber compositions of the invention, thecompositions do not contain curing agents, either because they areintermediate compositions to which a curing system will be, but not yethas been, added or because they are to be put in use without theaddition of curing agents in such applications as sealants, caulks,adhesives, etc.

As mentioned above, fillers may be and often are present in the uncuredrubber compositions of the present invention. Typical fillers includecarbon black in its various forms, glass, silica, talc, and similarlyfinely divided mineral materials. The amount of reinforcing fillerincorporated into the rubber compositions of the present invention maybe varied over a wide range although the mixture generally will containfrom about 30 to 100 parts of filler per 100 parts of rubber.

Carbon black fillers generally are included in the rubber compositionsof this invention, especially in the vulcanizates, and they include anyof the commonly available, commercially-produced carbon blacks. Thosehaving a surface area (EMSA) of at least 20 m² /g. and more preferablyat least 35 m² /g. up to 200 m² /g. or higher are preferred. Surfacearea values used in this application are those determined by ASTM testD-1765 using the cetyltrimethyl-ammonium bromide (CTAB) technique. Amongthe useful carbon blacks are furnace black, channel blacks and lampblacks. More specifically, examples of the carbon blacks include superabrasion furnace (SAF) blacks, high abrasion furnace (HAF) blacks, fastextrusion furnace (FEF) blacks, fine furnace (FF) blacks, intermediatesuper abrasion furnace (ISAF) blacks, semi-reinforcing furnace (SRF)blacks, medium processing channel blacks, hard processing channel blacksand conducting channel blacks. Other carbon blacks which may be utilizedinclude acetylene blacks. Mixtures of two or more of the above blackscan be used in preparing the rubber compositions of the invention.Typical values for surface areas of usable carbon blacks are summarizedin the following Table II.

                  TABLE II                                                        ______________________________________                                        Carbon Blacks                                                                 ASTM           Surface Area                                                   Designation    (m.sup.2 /g)                                                   (D-1765-82a)   (D-3765)                                                       ______________________________________                                        N-110          126                                                            N-220          111                                                            N-339          95                                                             N-330          83                                                             N-550          42                                                             N-660          35                                                             ______________________________________                                    

The carbon blacks utilized in the invention may be in pelletized form oran unpelletized flocculant mass. Preferably, for more uniform mixing,unpelletized carbon black is preferred. Similar silic reinforcing agentshaving comparable particle sizes and thus surface areas can also beused.

The following examples illustrate the preparation of the modifieduncured rubber compositions of the present invention. Unless otherwiseindicated in the examples or elsewhere in the application, all parts andpercentages are by weight, and the temperatures are in degreescentigrade. In the following examples, solution SBR-1 is an SBR in 37.5phr aromatic oil further characterized as containing 25% bound styreneand 2.5% max. block styrene, with a Mooney Viscosity: Large Rotor/4 at212° F. of 45±5.

Unless otherwise indicated, an internal mixer, such as a Brabender orsmall size Banbury mixer is used to prepare the uncured rubberformulations. The usual technique is to add various parts of thecomposition to the mixer, continuing the mixing for the indicated periodof time, and then making further additions. The standard technique isaccording to the following procedure.

    ______________________________________                                        Time          Add to Mixer                                                    ______________________________________                                        0             Polymer, 100 parts; preheat                                                   to 170° C.                                                             Half charge filler plus                                                       1-hydroxy benzimidazole                                                       3-oxide                                                         1.5           Balance of filler, zinc                                                       oxide and stearic acid                                          3.0           Processing oil                                                  6.0           Drop mixed compositions at                                                    160-170° C. (320-340° F.)                         ______________________________________                                    

Masterbatches prepared essentially according to this schedule can becombined with the conventional elastomer curing systems described in thefollowing examples in typical amounts and cured for 15-30 minutes atabout 150° C. to provide test specimens.

                  TABLE III                                                       ______________________________________                                        UNCURED RUBBER FORMULATIONS                                                   Example/pbw    Control    A       B                                           ______________________________________                                        Solution SBR-1 137.5      137.5   137.5                                       Carbon Black (N339)                                                                          63         63      63                                          ZnO            5          5       5                                           Stearic Acid   1.5        1.5     1.5                                         Product of Ex. 2                                                                             --         1.0     --                                          Product of Ex. 3                                                                             --         --      1.0                                         ______________________________________                                    

As mentioned above, the uncured modified rubber compositions of theinvention are useful in the preparation of filled vulcanizates which areuseful in a number of applications. Thus, the uncured modified rubbercompositions of the present invention generally are formulated withconventional rubber additives to form masterbatches (as in Examples Aand B above) which can then be cured by the addition of curing agents,accelerators, etc. When the uncured modified rubber compositions of thepresent invention are prepared in the absence of carbon black, carbonblack is added to the masterbatch formulation. Alternatively, when areinforcing filler such as carbon black is included in the mixture usedin the preparation of the uncured modified polymer rubber compositionsof the invention the addition of carbon black to the masterbatchformulation may be unnecessary if sufficient carbon black was includedin the initial mixture. If less than the desired amount of carbon blackis included in the initial mixture, then additional carbon black must beadded to the masterbatch. The total amount of carbon black included willrange from about 20 to 100 phr.

The vulcanizable compositions (including masterbatches) containing themodified rubbers of the present invention can be prepared byconventional techniques and using various types of mills, blenders andmixers known in the art.

The curing agents used to prepare the vulcanizates may be conventionaltypes such as sulfur- or peroxide-based curing systems. They are used inconventional amounts and incorporated in the uncured compositions of theinvention by known techniques and procedures. The vulcanizates of thisinvention are prepared by curing these compositions under conditions oftemperature and time customarily used in the art. Typically, the rubber,1-hydroxy-benzimidazole oxide or nitrogen- and oxygen-containingcompositions described herein, carbon black, other fillers and normalprocessing aids such as zinc oxide, stearic acid and processing oil aremixed, the sulfur and accelerators are then added, and the mixture iscured. Other mixing sequences can be used, but it is preferred to havethe rubber, 1-hydroxy-benzimidazole oxide or reaction product, andcarbon black composition intimately combined before vulcanizing agentsare added.

Among the desirable and beneficial properties exhibited by thevulcanized rubber compositions of the present invention prepared withthe modified rubber compositions described herein are an increase inrebound, reduced low strain hysteresis, higher electrical resistivityand when utilized in treads of tires, a decrease in the rolling loss andrunning temperature.

The following examples illustrate the preparation of vulcanized rubbercompositions in accordance with the invention utilizing the1-hydroxy-benzimidazole oxide modified rubbers of the invention.Conventional rubber compounding materials, conditions, temperatures,procedures and evaluation techniques are used unless noted to thecontrary.

EXAMPLE C

Passenger tire tread vulcanizates are prepared from a solution SBRaccording to a tread stock recipe containing 137.5 parts of SBR-1, 63phr of carbon black (N339), 5 phr of ZnO, 1.5 phr of stearic acid, 1.8phr of sulfur, 1.0 phr of Santocure NS, and 1.0 phr of the1-hydroxy-benzimidazole 3-oxide product of Example 2. A control stock isalso prepared containing no 1-hydroxybenzimidazole oxide. Theformulations are prepared and mixed at about 350° F. and thereaftercured in the usual manner. The vulcanizate specimens evaluated in anumber of standard tests. The results of the tests are summarized inTable IV.

                  TABLE IV                                                        ______________________________________                                                       Example:                                                                      Control                                                                             C                                                        ______________________________________                                        % Rebound                                                                     73° F.    46      52                                                   150° F.   60      62                                                   MTS 7% def.                                                                   10 lb. 10 HZ                                                                  K' (73° F.)                                                                             770     680                                                  K" (73° F.)                                                                             147     108                                                  Tan delta        0.191   0.159                                                % delta change   par     -17                                                  ______________________________________                                    

As can be seen, the use of the 1-hydroxybenzimidazole 3-oxide in ExampleC results in an increase in rebound and a 15% reduction in tan delta.

The vulcanizable and vulcanized rubber compositions of the inventionresulting from the use of the rubbers modified in accordance with thisinvention can be molded or shaped into the desired shapes by knowntechniques, and they can be used for many purposes for which similarcompositions are used. The vulcanized rubber compositions of theinvention exhibit improved mechanical properties such as reducedhysteresis (Tan delta and rebound), and when the rubbers of theinvention are utilized in the preparation of treads for tires, the tiresare characterized by a reduction in rolling loss. The entire tire may beconstructed of the SBR vulcanizates of the invention or other portionsin addition to the treads may be constructed using the vulcanizates ofthe invention.

In the practice of this invention, the tread can be applied during thebuilding of the green tire in which an uncured, shaped tread of theformulation of the present invention is built onto the carcass followingwhich the green tire is shaped and cured. Alternatively, the tread canbe applied to a cured tire carcass from which the previous tread hasbeen buffed or abraded away and the uncured, shaped tread of the presentinvention cured thereon as a retread.

While the invention has been described and exemplified herein byreference to specific examples, machinery, techniques, procedures andexamples, it is understood that it not restricted to any of these, andnumerous variations, combinations and permutations can be made withinthe scope of the invention as is clear to those skilled in the art.

We claim:
 1. A rubber composition comprising at least one rubber havingan unsaturated carbon chain and a minor property-improving amount of atleast one 1-hydroxy-benzimidazole 3-oxide compound of the formula##STR11## wherein R is hydrogen, or a, hydroxyl, lower acyl, lowerhydrocarbyl, lower hydrocarbyloxy, lower hydrocarbylthio, carboxyl,cyano, amino, amide or --C(O)-- lower hydrocarbyl group, and R' ishydrogen, or a lower hydrocarbyl, lower hydrocarbyl amide, carboxamidecarboxy acid, carboxy ester, or aryl group.
 2. The rubber composition ofclaim 1 wherein the rubber is NR, IR, BR, SBR, CR, CIIR, NIR or amixture of two or more of said rubbers.
 3. The rubber composition ofclaim 1 wherein the rubber is NR, SBR or a mixture containing at leastabout 50% of one of these, and R' is methyl.
 4. The rubber compositionof claim 1 wherein R is hydrogen, methyl, or methoxy.
 5. The rubbercomposition of claim 1 wherein the rubber is an uncured or vulcanizedrubber composition.
 6. The rubber composition of claim 1 wherein R' ishydrogen or a lower alkyl group.
 7. The rubber composition of claim 1wherein R is hydrogen and R' is methyl or phenyl.
 8. The rubbercomposition of claim 1 also containing at least one reinforcing filler.9. The rubber composition of claim 1 also containing at least one carbonblack filler.
 10. A rubber composition comprising at least one rubberhaving an unsaturated carbon chain and a minor property-improving amountof at least one nitrogen- and oxygen-containing composition obtained bythe reaction of a primary nitroalkane, a beta-ketosulfone, analpha-sulfonyl carboxylic ester, an alpha-sulfonyl carboxamide with abenzofurazan oxide in the presence of an alkali, said benzofurazan oxidebeing characterized by the formula ##STR12## wherein R is hydrogen, ora, hydroxyl, lower acyl, lower hydrocarbyl, halohydrocarbyl lowerhydrocarbyloxy, lower hydrocarbylthio, carboxyl, cyano, amino, amide or--C(O)-- lower hydrocarbyl group.
 11. The rubber composition of claim 10wherein the rubber is NR, IR, BR, SBR, CR, CIIR, NIR or a mixture of twoor more of said rubbers.
 12. The rubber composition of claim 10 whereinthe rubber is NR, SBR or a mixture containing at least about 50% of oneof these.
 13. The rubber of claim 10 wherein the rubber composition isan uncured or vulcanized rubber composition.
 14. The rubber compositionof claim 10 wherein R is hydrogen, methyl, or methoxy.
 15. The rubbercomposition of claim 10 wherein the primary nitroalkane of the formula

    R'CH.sub.2 NO.sub.2

wherein R' is hydrogen or a lower alkyl, hydrocarbyl amide or carboxylicester group.
 16. The rubber composition of claim 10 wherein thebeta-ketosulfonyl group is of the formula

    PhSO.sub.2 CR'HC(O)Ph

wherein R' is hydrogen or a lower hydrocarbyl group, and thealpha-sulfonyl carboxylic acid ester and carboxamide are of the formula

    PhSO.sub.2 CH.sub.2 R'

wherein R' is an amide, substituted amide, a carboxylic acid orcarboxylic ester.
 17. The rubber composition of claim 10 also containingat least one reinforcing filler.
 18. The rubber composition of claim 11also containing at least one carbon black filler.
 19. A filledvulcanizate of a rubber composition comprising at least one rubberhaving an unsaturated carbon chain, a minor property-improving amount ofat least one 1-hydroxy-benzimidazole-3-oxide compound of the formula##STR13## wherein R is hydrogen, or a halogen, hydroxyl, lower acyl,lower hydrocarbyl, lower hydrocarbyloxy, lower hydrocarbylthio,carboxyl, cyano, amino, amide or --C(O)-- lower hydrocarbyl group, andR' is hydrogen, or a lower hydrocarbyl, lower hydrocarbyl amide,carboxamide carboxy acid, carboxy ester, or aryl group and at least onefiller.
 20. The vulcanizate of claim 19 wherein the rubber is NR, SBR ora mixture containing at least about 50% SBR, and the filler is carbonblack, silica or a mixture of these.
 21. The vulcanizate of claim 19wherein the filler is at least one reinforcing carbon black.
 22. Thevulcanizate of claim 19 wherein R' is methyl.
 23. The vulcanizate ofclaim 19 wherein R is hydrogen and R' is methyl.
 24. The rubbercomposition of claim 10 wherein the rubber composition is a filledvulcanizate containing at least one filler.
 25. The filled vulcanizateof claim 24 wherein the filler is at least one carbon black.
 26. Arubber composition comprising at least one rubber having an unsaturatedcarbon chain and from about 0.01 to about 5 parts by weight phr of atleast one 1-hydroxybenzimidazole 3-oxide compound of the formula##STR14## wherein R is hydrogen, or a halogen, hydroxyl, lower acyl,lower hydrocarbyl, lower hydrocarbyloxy, lower hydrocarbylthio,carboxyl, cyano, amino, amide or --C(O)-- lower hydrocarbyl group, andR' is hydrogen, or a lower hydrocarbyl, lower hydrocarbyl amide,carboxamide carboxy acid, carboxy ester, or aryl group.
 27. A rubbercomposition comprising at least one rubber having an unsaturated carbonchain and from about 0.01 to about 5 parts by weight phr of at least onenitrogen- and oxygen-containing composition obtained by the reaction ofa primary nitroalkane, a beta-ketosulfone, an alpha-sulfonyl carboxylicester, an alpha-sulfonyl carboxamide with a benzofurazan oxide in thepresence of an alkali, said benzofurazan oxide being characterized bythe formula ##STR15## wherein R is hydrogen, or a halogen, hydroxyl,lower acyl, lower hydrocarbyl, halohydrocarbyl lower hydrocarbyloxy,lower hydrocarbylthio, carboxyl, cyano, amino, amide or --C(O)-- lowerhydrocarbyl group.
 28. The vulcanizate of claim 19 wherein the rubbercomposition contains from about 0.01 to about 5 parts by weight phr ofthe benzimidazole-3-oxide compound.